Documentation Index
Fetch the complete documentation index at: https://docs.crazyrouter.com/llms.txt
Use this file to discover all available pages before exploring further.
Responses Function Calling
As of March 23, 2026, Crazyrouter production has verified that gpt-5.4 on the Responses API reliably returns function_call.
Claude does not currently support POST /v1/responses. If you need Claude tool calling, use POST /v1/messages or POST /v1/chat/completions.
Step 1: Let the Model Produce a Function Call
curl https://crazyrouter.com/v1/responses \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_API_KEY" \
-d '{
"model": "gpt-5.4",
"input": "What is the weather in Beijing? Use the tool.",
"tools": [
{
"type": "function",
"name": "get_weather",
"description": "Get weather info for a city",
"parameters": {
"type": "object",
"properties": {
"city": {"type": "string"}
},
"required": ["city"],
"additionalProperties": false
}
}
]
}'
{
"output": [
{
"type": "function_call",
"name": "get_weather",
"arguments": "{\"city\":\"Beijing\"}"
}
]
}
Once you receive the function_call, send your actual tool result back as function_call_output:
{
"model": "gpt-5.4",
"input": [
{
"type": "function_call",
"call_id": "call_123",
"name": "get_weather",
"arguments": "{\"city\":\"Beijing\"}"
},
{
"type": "function_call_output",
"call_id": "call_123",
"output": "{\"temperature\":22,\"condition\":\"sunny\"}"
}
],
"tools": [
{
"type": "function",
"name": "get_weather",
"description": "Get weather info for a city",
"parameters": {
"type": "object",
"properties": {
"city": {"type": "string"}
},
"required": ["city"],
"additionalProperties": false
}
}
]
}
This page keeps only the function_call path that was reproduced in production. For more complex multi-tool chains or streamed argument deltas, revalidate on the same day before depending on them.
